Nuxeo's data providers should support deployment inside or outside an EJB container. The following describe what should be
achieved for each use case.

Outside an EJB container

In that case, the framework resolves the service as the document rating provider.
A persistence provider is lazy obtained using nuxeo persistence core services and used
for getting access to the entity manager.

Inside an EJB container

In that case, the framework is resolving the service using the document rating bean.
The persistence unit is initialized by the container himself, and an entity manager is
automatically injected into the bean. The entity manager is transmitted by the bean to the
core provider using a call parameter (thread safe).